Figure S2.

Sub-volume averaging of thick filaments, related to Figures 3 and 5

(A) Slice through a tomogram depicting three adjacent thick filaments. Scale bar, 50 nm.

(B) Averaged structure from a global refinement. The map suffers from missing wedge artifacts, indicating alignment focused on the missing wedge instead of actual structural features.

(C) The distribution of myosin heads when retracted to the thick filaments in the relaxed state has a C3 symmetry. We therefore performed a refinement and reconstruction applying C3 symmetry. However, this did not improve the quality of the map, indicating that the core of vertebrate thick filaments is not C3 symmetric.

(D) A local refinement with restricted possible rotation angles reduced alignment errors and thereby missing wedge artifacts. This reconstruction was used as a model for thick filament in Figures 3 and 5.

(E) The estimated resolution of the reconstruction in (D) is 30.4 Å using the 0.143 criterion.